Photosensitive drums incorporated into image forming apparatuses, such as printers, copiers, and facsimile machines, are used for electrical charging, exposure, development, and transfer in electrophotographic process. A great number of techniques have already been suggested to reduce vibrations occurring on such a photosensitive drum. For example, techniques as described in Patent Documents 1 and 2 noted below have been suggested.
Patent Document 1 describes a technique in which a stiffness of a cylindrically shaped photosensitive drum is determined in such a manner that a natural frequency of the photosensitive drum becomes higher than a frequency of an exciting force. This is a technology contemplated with a view toward avoiding resonance that occurs when the natural frequency of the photosensitive drum matches with the frequency of the exciting force.
Patent Document 2 describes a photosensitive drum in which a filler such as that formed of aluminum, for example is embedded (refer to FIG. 3 in Patent Document 2). This is a technology contemplated with a view toward increasing a weight and a stiffness of the photosensitive drum by means of the embedded filler, to thereby reduce vibrations of the photosensitive drum.